Intermetallic Pd-Y nanoparticles/N-doped carbon nanotubes as multi-active catalysts for oxygen reduction reaction, ethanol oxidation reaction, and zinc-air batteries.

Intermetallic nanomaterials are unique in terms of their band gap, atomic-level arrangement, and well-defined stoichiometry, which allows them to exhibit significantly enhanced catalytic performance in electrochemical applications. However, the preparation of durable intermetallic catalysts with a lower content of platinum group metals is challenging, while the lack of control over the loss of active components limits their long-term application due to weak interaction between the support and the nanostructure. Here, we have designed the intermetallic alloyed nanoparticles (NPs) of PdY on N-doped carbon nanotubes (PdY/NCNTs) as a multifunctional catalyst for the oxygen reduction reaction (ORR), the ethanol oxidation reaction (EOR), and zinc-air batteries (ZABs). The strong adhesion through nitrogen ensures the anchoring of alloyed PdY NPs on the NCNTs, which restrains atomic migration and sintering during their conversion to intermetallic phases. This study confirms that there is negligible active site leaching owing to the strong and multiple dative bonds between the NCNTs and PdY NPs. Therefore, this catalyst exhibits remarkable catalytic activity, resulting in a mass activity of 1317 and 2902 mA mgPd-1 at jk and jf for the ORR and the EOR, respectively, and remains stable for a longer period. In addition, the PdY/NCNT-containing air cathode-fabricated ZAB achieved a higher power density (0.236 W cm-2) compared to the benchmark Pt/C.

Cobalt-Catalyzed Formation of Grignard Reagents via C-O or C-S Bond Activation.

C(aryl)-OMe bond functionalization catalyzed by cobalt(II) chloride in combination with a nacnac-type ligand and magnesium as a reductant is reported. Borylation and benzoylation of aryl methoxides are demonstrated, and C(aryl)-SMe bond borylation can be achieved under similar conditions. This is the first example of achieving these transformations using cobalt catalysis. Mechanistic studies suggest that a Grignard reagent is generated as an intermediate in a rare example of a magnesiation via a C-O bond activation reaction. Indeed, an organomagnesium species could be directly observed by electrospray ionization mass spectroscopic analysis. Kinetic experiments indicate that a heterogeneous cobalt catalyst performs the C-O bond activation.

Highly efficient Ag doped δ-MnO2 decorated graphene: Comparison and application in electrochemical detection of H2O2.

Cytotoxic H2O2 is an inevitable part of our life, even during this contemporary pandemic COVID-19. Personal protective equipment of the front line fighter against coronavirus could be sterilized easily by H2O2 for reuse. In this study, Ag doped δ-MnO2 nanorods supported graphene nanocomposite (denoted as Ag@δ-MnO2/G) was synthesized as a nonenzymatic electrochemical sensor for the sensitive detection of H2O2. The ternary nanocomposite has overcome the poor electrical conductivity of δ-MnO2 and also the severe aggregation of Ag NPs. Furthermore, δ-MnO2/G provided a rougher surface and large numbers of functional groups for doping more numbers of Ag atoms, which effectively modulate the electronic properties of the nanocomposite. As a result, electroactive surface area and electrical conductivity of Ag@δ-MnO2/G increased remarkably as well as excellent catalytic activity observed towards H2O2 reduction. The modified glassy carbon electrode exhibited fast amperometric response time (<2 s) in H2O2 determination. The limit of detection was calculated as 68 nM in the broad linear range (0.005-90.64 mM) with high sensitivity of 104.43 µA mM-1 cm-2. No significant interference, long-term stability, excellent reproducibility, satisfactory repeatability, practical applicability towards food samples and wastewater proved the efficiency of the proposed sensor.

Pyrrolinium-Substituted Persistent Zwitterionic Ferrocenate Derivative Enabling the Application of Ferrocene Anolyte.

Here, we report the imidazolium-/pyrrolinium-substituted persistent zwitterionic ferrocenate derivatives, which were characterized by electron paramagnetic resonance (EPR) and 57Fe Mössbauer spectroscopy. Additional theoretical studies on these zwitterionic ferrocenate derivatives clearly explain the origin of their thermal stability and the orbital interactions between iron and imidazolium-/pyrrolinium-substituted zwitterionic cyclopentadienyl ligand. Exploiting the facile Fe(II/I) redox chemistry, we successfully demonstrated that the pyrrolinium-substituted ferrocene derivative can be applied as an example of derivatized ferrocene anolyte for redox-flow batteries. These zwitterionic ferrocenate derivatives will not only deepen our understanding of the intrinsic chemistry of ferrocenate but have the potential to open the way for the rational design of metallocenate derivatives for various applications.

Cobalt-Catalyzed C-F Bond Borylation of Aryl Fluorides.

A mild and practical cobalt-catalyzed defluoroborylation of fluoroarenes is presented for the first time. The method permits straightforward functionalization of fluoroarenes, with high selectivity for borylation of C-F over C-H bonds, and a tolerance for aerobic conditions. Furthermore, two-step 18F-fluorination was achieved for expanding the scope of 18F-positron emission tomography probes.

The insight study of SnO pico size particles in an ethanol-water system followed by its biosensing application.

Pico sized Stannous oxide particles (SnO PPs) were synthesized in an ethanol-water solvent system on the surface of nitrogen doped graphene oxide (GO). The highly conductive support was a combination of dual interactions between 4-aminomethylbenzylamine (AMBA) and GO. The oppositely positioned -NH2 linkers of the AMBA were covalently incorporated into the GO matrix through condensation reaction followed by the strong π - π stacking interactions between aromatic rings of AMBA and GO. The change in the local chemical environment of GO via dual interactions provided a suitable atmosphere for the growth and dispersion of SnO PPs on GO-AMBA surface. The possible mechanism for the formation of SnO in an ethanol-water solvent system was evaluated. Furthermore, a light was shed on the factors responsible for the pico size of SnO particles synthesis along with its phenomenal distribution on the GO-AMBA surface. The catalyst containing SnO PPs was deployed as a biosensor for the detection of ascorbic acid (AA) for the very first time. A very wide linear range of 5.0 × 10-5-7.0 × 10-3 M, limit of detection (LOD) of 1.19 × 10-5 M along with excellent practical feasibility, storage stability, repeatability and selectivity towards AA electrooxidation showed the excellent synergy between nitrogen-rich GO surface and SnO PPs. The sensitivity (885.54 µAmM-1cm-2) of the catalyst was the most attractive feature, as it was obtained in the presence of 5 and 2-fold higher concentration of UA and DA interfering species respectively.

Highly Efficient Dual Active Palladium Nanonetwork Electrocatalyst for Ethanol Oxidation and Hydrogen Evolution.

Tunable palladium nanonetwork (PdNN) has been developed for catalyzing ethanol oxidation reaction (EOR) and hydrogen evolution reaction (HER) in alkaline electrolyte. 3D PdNN is regarded as a dual active electrocatalyst for both EOR and HER for energy conversion application. The PdNN has been synthesized by the simple chemical route with the assistance of zinc precursor and a surfactant (i.e., cetyltrimethylammonium bromide, CTAB). The thickness of the network can be tuned by simply adjusting the concentration of CTAB. Both EOR and HER have been performed in an alkaline electrolyte, and characterized by different voltammetric methods. The 3D PdNN has shown 2.2-fold higher electrochemical surface area than the commercially available Pt/C including other tested catalysts with minimal Pd loading. As a result, it provides a higher density of EOR and HER active sites and facilitated the electron transport. For example, it shows 2.6-fold higher mass activity with significantly lower CO2 production for EOR and the similar overpotential (110 mV @ 10 mA cm-2) for HER compared to Pt/C with better reaction kinetics for both reactions. Thus, the PdNN is proved as an efficient electrocatalyst with better electrocatalytic activity and stability than state-of-the-art Pt/C for both EOR and HER because of the crystalline, monodispersed, and support-free porous nanonetwork.

New Approach for Porous Chitosan-Graphene Matrix Preparation through Enhanced Amidation for Synergic Detection of Dopamine and Uric Acid.

Amide-functionalized materials have emerged as promising nonprecious catalysts for electrochemical sensing and catalysis. The covalent immobilization of chitosan (CS) onto graphene sheet (GS) (denoted as CS-GS) has been done via higher degree of amidation reaction to develop an electrochemical sensing matrix for simultaneous determination of dopamine (DA) and uric acid (UA). The enhanced amidation between CS and GS has not been reported previously. However, electrochemical results have revealed that the CS-GS enhances the electrocatalytic performance in terms of the oxidation potential and peak current due to the higher degree of amide functionalization compared to that of CS/GS, which has a lower amidation. Differential pulse voltammetry-based studies have indicated that the CS-GS matrix works at a lower detection limit (0.14 and 0.17 µM) (S/N = 3) and over a longer linear range (1-700 and 1-800 µM), with a comparatively higher sensitivity (2.5 and 2.0 µA µM-1 cm-2), for DA and UA, respectively. In addition, the CS-GS matrix demonstrates good selectivity toward the detection of DA and UA in the presence of a 10-fold higher concentration of AA and glucose. The as-prepared three-dimensional porous CS-GS also endows selective determination toward DA and UA in various real samples.

Electrochemical Sensing of Monohydric Alcohols on Different Linkers Imbedded in Between Graphene and Platinum Nanoparticles.

We investigated the relationship between the linker's length and the electrooxidation of methanol and ethanol with PtNPs-decorated graphene oxide (GO). The covalently functionalized materials were prepared with three different lengths of the alkane chain as the linker molecules in between GO and platinum nanoparticles (PtNPs). Electrochemically reduced GO-S-(CH2)n-S-Pt [ERGO-S-(CH2)n- S-Pt, wherein n = 2, 3 and 4] was obtained via electrochemical reduction of GO-S-(CH2)1-S-Pt in PBS at pH 5. ERGO-S-(CH2)n-S-Pt was characterized by XPS and FE-SEM. The XPS result reveals that the Pt at% increased with the increasing of chain length and the surface morphology indicates the surface area increased with the increasing of linker's length. The electrochemical behavior of these modified glassy carbon electrodes (GCEs) were investigated using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry (CA). The ERGO-S-(CH2)n-S-Pt was employed to detect methanol and ethanol; and the ERGO-S-(CH2)4-S-Pt showed a better performance towards alcohol oxidation reaction (AOR) among all ERGO-S-(CH2)n- S-Pt. The detection limit of methanol and ethanol was 1.8 x 10⁻² mM and 1.28 x 10⁻² mM, respectively, at ERGO-S-(CH2)4-S-Pt.

Synthesis of Electrochemically Reduced Graphene Oxide Bonded to Thiodiazole-Pd and Applications to Biosensor.

A novel biosensor for the determination of hydrogen peroxide and glucose was developed based on EGN-TDZ-Pd, as an electrocatalyst. The preparation of graphene oxide (GO) nanosheets was functionalized by combining it with 5-amino-1,3,4-thiadiazole-2-thiol (TDZ) and by covalently bonding it to palladium (Pd) nanoparticles (GO-TDZ-Pd). In the electrochemical investigation, EGN-TDZ-Pd was characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) and chronoamperometry (CA) were used to characterize the performance of EGN-TDZ-Pd. The proposed H2O2 biosensor exhibited a wide linear range from 10 µM to 6.5 mM. Also, a glucose biosensor was prepared using glucose oxidase and EGN-TDZ-Pd placed onto a glassy carbon electrode (GCE). The GOx/EGN-TDZ-Pd/GCE was easily prepared using a rapid and simple procedure, and it was utilized for highly sensitive glucose determination.

Manganese Dioxide/Reduced Graphene Oxide with Poly(3,4-ethylenedioxythiophene) for Improved Electrocatalytic Oxygen Reduction Reaction.

Poly(3,4-ethylenedioxythiophene)-(PEDOT)-functionalized reduced graphene oxide (rGO) with MnO2 nanoparticles (MnO2/PEDOT/rGO) was prepared using electrochemical methods. The MnO2/ PEDOT/rGO was obtained through the electrochemical reduction of PEDOT/GO and under electrochemical treatment in KMnO4. The PEDOT/rGO and MnO2/PEDOT/rGO were characterized by several instrumental and electrochemical methods. The electrocatalytic 02 reduction for both electrodes was investigated via cyclic and hydrodynamic voltammetry in 0.1 M KOH aqueous solutions. The kinetic analysis in comparison to PEDOT/rGO a significant enhancement was found for the MnO2/PEDOT/rGO. The proposed main path in the oxygen reduction reaction (ORR) mechanism on the MnO2/PEDOT/rGO was the direct four-electron transfer process with faster transfer kinetic rate. The better ORR kinetics were obtained due to the excellent composite formation and well attachment of MnO2 NPs within oxide form. The PEDOT/rGO was less stable for long term use than MnO2/PEDOT/rGO.

Electrocatalytic Oxidation of Formic Acid in an Alkaline Solution with Graphene-Oxide- Supported Ag and Pd Alloy Nanoparticles.

The electrocatalytic activities of metal-decorated graphene oxide (GO) catalysts were investigated. Electrochemically reduced GO-S-(CH2)4-S-Pd [ERGO-S-(CH2)4-S-Pd] and GO-S-(CH2)4-S-PdAg alloy [ERGO-S-(CH2)4-S-PdAg] were obtained through the electrochemical reduction of GO-S-(CH2)4-S-Pd and GO-S-(CH2)4-S-PdAg in a pH 5 PBS solution. It was demonstrated that the application of ERGO-S-(CH2)4-S-Pd and ERGO-S-(CH2)4-S-PdAg used in a modified GCE improves the electrocatalytic oxidation of formic acid. The addition of an Ag nanoparticle with a carbon chain-Pd in the electrode provides an electrode with very interesting properties for the electrocatalytic oxidation of formic acid. The ERGO-S-(CH2)4-S-Pd and ERGO-S-(CH2)4-S-PdAg were characterized via X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). ERGO-S-(CH2)4-S-Pd and ERGO-S-(CH2)4-S-PdAg can be employed for the electrocatalytic oxidation of formic acid. The electrochemical behaviors of this electrode were investigated using cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS).

High catalytic activity of electrochemically reduced graphene composite toward electrochemical sensing of Orange II.

Orange II, an azo dye, is sometimes illegally used as a red dye in food products despite its adverse health effects if consumed. Therefore, the determination of low concentrations of Orange II is an important target. An Orange II sensor was prepared using electrochemically reduced graphene oxide grafted with 5-amino-1,3,4-thiadiazole-2-thiol-Pt nanoparticles (denoted as ERGO-ATDT-Pt) onto a glassy carbon electrode (GCE) and investigated for Orange II detection in 0.1M acetate buffer solution (ABS at pH 4.5) with prominent reversible redox peaks. A wide linear range of 1×10(-)(8)-6×10(-)(7)M with a low detection limit of 3.4×10(-)(10)M (s/n=3) was found for Orange II detection. This developed ERGO-ATDT-Pt/GCE sensor showed good selectivity, excellent stability and better response to the real sample analysis with excellent recovery.

Characteristic electronic perturbation by asymmetric arrangements of p-aminophenyl substituents in free-base porphyrins.

We have investigated the perturbed electronic properties of meso-substituted free-base porphyrins with symmetric and asymmetric arrangements of substituents using time-resolved spectroscopic measurements and theoretical calculations. The extent of electronic perturbation by substituents in meso-substituted porphyrins is mainly affected by the isoenergetic condition of frontier MOs of porphine and substituent units, nonorthogonal geometry, and geometrical arrangement of substituents. By using the asymmetric arrangements of p-aminophenyl and pentafluorophenyl substituents, we can induce the electron-rich condition on the porphine unit and the intramolecular charge transfer character in the excited state. On the basis of this work, we can gain further insight into the energetic and geometric factors of substituents, the interaction between porphine and substituent units, and the perturbed photophysical and electronic properties by substituents, which provides a firm basis for further understanding of the catalytic activities or photophysical properties of porphyrins in porphyrin-based molecular catalysts and electronics.

Electrochemical sensing of H2O2 by the modified electrode with pd nanoparticles on multi-walled carbon nanotubes-g-poly(lactic acid).

A simple method has adapted to prepare MWCNT grafted Poly(lactic acid) (MWCNT-g-PLA) by intercalative polymerization of poly(lactic acid) in the presence of multi-wall carbon nanotubes (MWCNT) functionalized with hydroxyl groups. The functionalized MWCNT has obtained from the treatment of methylene diphenyl diisocyanate (MDI) with MWCNT, and then the reaction with 1,4-butanediol (BD) to create functional hydroxyl groups. MWCNT-g-PLA-Pd and MWCNT-g-PLA-Pt have prepared from the MWCNT-g-PLA and metal precursors. The synthesized materials have characterized by 1H-NMR, Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). The MWCNT-g-PLA-Pd is possibilities for employing to electrochemical detection of hydrogen peroxide. Electrocatalytic activities are verified from cyclic voltammetry (CV) and amperometric response in 0.1 M phosphate buffer solution (PBS). The biosensor provided good stability and selectivity towards interferences such as UA, AA, and glucose.

A green preparation of nitrogen doped graphene using urine for oxygen reduction in alkaline fuel cells.

A simple, eco-friendly and efficient harmless chemical approach has been developed for the simultaneous nitrogen (N) doping and reduction of graphene oxide (GO) by cost free human urine using simple refluxing. Large-scale preparation of graphene has been hindered largely by several issues, such as highly toxic reducing agents that are harmful to human health and environment, complicated reduction process and costly chemicals. Human urine is a natural precursor of urea with no cost. In this process, the NH3 has acted as not only reducing but also doping agent that produced via thermal decomposition of urea, while the N doping level of ~11.1 at% is achieved. For the first time we have used urine as a reductant and doping agent in such a high class chemical technology. The simultaneous reduction and N-doping of GO using urine (denoted as UNG) have confirmed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and UV-vis spectroscopy. The resultant UNG has demonstrated to show remarkable electrocatalytic activity toward oxygen reduction reaction (ORR) with better fuel selectivity, and stability than that of the commercially available 20 wt% Pt/C electrode using cyclic voltammetry (CV) and chronoamperometry.

The nanostructure of nitrogen atom linked carbon nanotubes with platinum employed to the electrocatalytic oxygen reduction.

Multi-walled carbon nanotube grafted Pt nanoparticles via nitrogen atom (MWCNT-N-Pt) has chemically synthesized and characterized as an efficient oxygen reduction reaction (ORR) catalysts. Structural and morphological properties of the electrocatalyst have characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) techniques. The electrochemical properties have evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and hydrodynamic voltammetry techniques. The electrochemical properties toward ORR of MWCNT-N-Pt have evaluated in 0.1 mol L(-1) HClO4 aqueous solution. The electrocatalytic reduction of O2 at the MWCNT-N-Pt catalyst establishes a pathway of four-electron transfer reduction into H2O. Hydrodynamic voltammetry reveals that the modified electrode has catalyzed effectively at higher potential. The value of transferred electron number and other kinetic parameters have demonstrated that the MWCNT-N-Pt is highly facilitated than that of bulk Pt to electrocatalytic oxygen reduction with comparatively low Pt content (27.04 Wt%) and higher electrochemical surface area (ESA(Pt)) 94.34 m2 gPt(-1).

Electrocatalytic reduction of H2O2 on thiolate graphene oxide covalently to bonded palladium nanoparticles.

The electrocatalytic reduction of hydrogen peroxide on thioalted graphene oxide (t-GO) covalent bonded to palladium nanoparticles was used as the basis of an H2O2 biosensor. Poly (diallydimethylammonium chloride)-coated t-GO-Pd on glassy carbon electrodes was easily and quickly prepared and gave sensitive measurements of H2O2 concentration. The Pd nanoparticles covalently bonded to the thiolated graphene oxide were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy. Comparable results for H2O2 determination were obtained from cyclic voltammetric and amperometric measurements. The proposed H2O2 biosensor exhibited a wide linear range of 10 microM to 10 mM, and a low detection limit of 0.22 microM (S/N = 3), at an applied potential of -0.1 V by the amperometric method.

Simultaneous determination of serotonin and dopamine at the PEDOP/MWCNTs-Pd nanoparticle modified glassy carbon electrode.

Electrochemical determination of dopamine (DA) and serotonin (5-HT) have been studied at a modified glassy carbon electrode (GCE) in 0.1 M phosphate buffer solution (PBS) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) at pH 7.4, all over the interfering biomolecule ascorbic acid (AA). The GCE was modified by palladium-functionalized, multi-walled carbon nanotubes (MWCNTs-Pd) with electrochemical deposition of poly 3,4-ethylenedioxy pyrrole (PEDOP), denoted as PEDOP/MWCNTs-Pd/GCE, and investigated by SEM and EIS experiments. The highly electrocatalytic activity of the modified electrode toward 5-HT and DA was demonstrated from the sensitive and well-separated voltammetric experiment. The oxidation peaks found were 0.165 and 0.355 mV for DA and 5-HT, respectively. The composite film shows a significant accumulation effects on two species, as well as the mutual interference among the analytes. This biosensor was best in response compared to other modified electrodes made in the same lab. The lowest detection limits were found to be 5.0 x 10(-9) and 1.0 x 10(-8) for 5-HT and DA, respectively. The respective linear ranges were determined as 1.0 x 10(-7) to 2.0 x 10(-4) and 1.0 x 10(-7) to 2.0 x 10(-4) for 5-HT and DA.

Wind-drag estimation in a traffic accident involving a motor scooter and a tractor-trailer.

This case report describes a noncontact traffic accident involving a motor scooter and a tractor-trailer with a focus on the wind-drag effect. We used load cells to measure the drag force acting on a substantially similar motor scooter when a substantially similar tractor-trailer passes by it, taking into consideration various speeds of the tractor-trailer and distances between the two vehicles. A three-dimensional steady-state flow analysis was also performed by using the CFX program for computational fluid dynamics to examine the streamlines and the pressure distribution around the tractor-trailer at various speeds. From the experiment, for a separation distance of 1.0 m (3.28 ft) and a speed of 90 km/h (55.9 mph), the maximum resultant drag force is 124.5 N (28 lb); this constitutes a degree of force that could abruptly disrupt the stability in maneuvering by an operator who is unaware of the approaching tractor-trailer. In addition, a single equation that relates the tractor-trailer speed to the drag force that acts on the motor scooter was derived on the basis of the Reynolds number (Re) and the wind-drag coefficient (C(d)): C(d) = 1.298 × 10(-7) Re.